Decimal-point calculator



Nov. 20, 1923.

C. E. LATSHAW DECIMAL POINT CALCULATOR Filed Aug. '7. 1922 means 01- THE PROD Char/a5 EZOZEV/Idh tiplication.

Patented Nov. 20, 1923.

PATENT OFFICE.

CHARLES E. LATSHAW, OF-MINNEAPOLIS, MINNESOTA.

.DECIMAL-POIN'I CALC LATOR.

Application filed August 7, 1922. Serial No. 580,124.

To all whom it may concern:

Be it known that 1, CHARLES E. LATSHAW, a citizen of the United States, residing at Minneapolis, in the county of Hennepin and State of Minnesota, have invented certain new and useful Improvements in Decimal- Point Calculators; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to whichit appertains to make and use the same.

My invention provides what may be appropriately designated either as a decimal point calculator or as a decimal dial, and is in the nature of an improvement on or refinement of the decimal dial disclosed and broadly claimed in my prior Patent No. 1,301.110, issued April 22, 1919.

A device of the above character serves to enable the, operator to very quickly locate the decimal point in making computations such as multiplication, regardless useful purpose is foundin connection with adding or computing machines, computing slide rules, and the like, and as a check in locating the decimal point in logarithm.

Adding machines, asis well known, are primarily constructed to perform the function of addition, and machinesfthat list the items are generally equipped with keys for repeating. By the use of the repeater key, items are duplicated a plural number of times without rewriting the number on the keyboard. In performing multiplication with a multiplier composed of several digits, the items are repeated the required number of times, first in the tens, then in the hun-.

dreds, then in the thousands column, and so on. This form of addition is termed mul- Multiplying from right'to left on the adding machines is very limited unless the machine is of very large capacity.

A person familiar with adding machine operations finds it: very easy to multiply from left to right; but when using whole numbers followed by decimals, problems are found where the product is so large that themachine is not large enough to give correct results.

\Vhereas, by reversing the operation and multiplying from left to right, the prodnot Will'be substantially correcteven when some of the right-hand numerals beyond the decimal point'are' dropped out of the computation. 'The dropping of these numbers at the right'of theldecimalpoint'makes of how such computations are made; but its mostv it very diflicult to mentally determine the proper location for the decimal point in the product. The device of my prior patent and more particularly the device of my present application, as already indicated, enables an operator to quickly determine the proper location of the decimal point in the product.

The particular device specifically disclosed in my prior patent as a concrete example of one form of my invention therein broadly claimed, the arrangement is such that the position of the decimal point in the product was determined by arelation of the digits in the multiplier and in the multiplicand; but in my present device I obtain in a simpler manner with much greater accuracy and a more comprehensive arrangement in the product preferably is determined by a relation of the digits in the multiplicand and in the product itself.

A preferred form of the present invention is illustrated in the accompanying drawings wherein like characters indicate like parts throughout the several views.-

Reterring to the drawings:

Fig. 1 is a plan view of the improved decimal point indicator;

Fig. 2 is a vertical section on the line 2-2 of Fig. 1; I a

Fig. 3 is a diagrammatic view showingthe arrangement of the keys of a commercial adding machine having a keyboard of the ten-key type, representing the digits 1, 2, 3, 4, 5, 6, 7, 8, 9, O; and

Fi 4 illustrates an arrangementin which the front surface of the case of an adding machine of theabove noted character is utilized as the base plate of my improved decimal point calculator.

Here it may be stated that this indicator more particularly will be found usedin connection with the simpler forms ofadding machines such as the commercial machine above noted.

In Fig. 3 the ten digitkeys ofan adding machine are marked in theusual way by the numerals 1.. 2, 3, 41, 5.6, 7, 8, 9,0. l i

In Figs. 1 and 2, the base plate of the calculator is indicated by the numeral 11 and is there shown as an independent plate having gins with the first left-hand 180 degrees of the circumference thereof, and the base plate ll is similarly marked with digits 0 to 9, inclusive, correspondingly spaced. On the lelthaud side of said base plate is marked with the words Zone of one less," and with several circiunifcrentially spaced minus marks. At its rightdiand side, said base plate is marked Equal number Zone and with several circumtenmtially spaced equality (2) marks. Also the dial is marked with a radially extended arrow 1e, and the base plate 11 is marked with reversely turned upper arrows l5 and revers .L tended lower arrows 16. The dial 13 is prel erably provided with an operating knob 1'7. In Fig. 4 the base plate 11 there illustrated is one of the front plates 01'? the l: ys ot an adding machine, which latter is indicated as an entirety by the numeral 18.

OPERATION.

The use of the device above described is substantially as follows:

Reverse or backward multiplication befigrure of both the multiplicand and the multiplier. Hence, the revision of the old method is obvious. This decimal and integral place calculator is a device for instantly locating a decimal point when using any adding, listing or non listing; machine as well as slide rules that are practical for multiplying from left to right. It provides a simple method for correctly locating the decimal point when multiplying integers followed by endless numbers olt' decimals. lVhen whole numbers are found in both the multiplicand and the multiplier whole numbers are multiplied by decimals or pure decimals by pure decimals, as directed.

First: Count all the whole numbers in the problem; that is, all integral places in both the multiplicand and the multiplier, and disregard the decimals Following whole numbers, for the reason that the decimal point is determined by the number of integral places in the problem, and the decimals or fractions are disregarded.

Second: Select the first the multiplicand inp; dial.

Third: Complete the ])l()l')l0lll, then turn the dial until the selected d git of the multiplicand is opposite to the first left-hand digit of the quotient or product. Be it understood that all digits of the multiplicand are vfound on the revolving dial and all digits of the product are found on the base to which the dial is fastened.

Fourth: The arrow digit to the left of and locate it on the rcvolv on the revolving dial will point to either Next figures or to the Zone of equal numbers or to Zone of minus one. The arrow will point to the words Next figures only when the first digit of the multiplicand and the first digit of the product are one and the same. In that case the next two figures of the multiplicaiul and the product; are compared as above explained.

Fifth: When the arrow points to Zone of equal numbersj place the decimal point as many places from the left of the product as there are Whole numbers in the problem, and when Zone of minus one is pointed out by the arrow, place the decimal point one less place from left of product than there are whole numbers in the problem, always reckoning from left to right.

Dec hauls decimals.

Proceed as above by selecting first digit to left or" multiplicand and product and since ciphers followed by a decimal point and be tween the first digit are minus or negative places, it follows that when the arrow points to Zone minus one. that one additional cipher must be added to the product. When arrow points to Equal number zone, simply prefix product with as many ciphers as there are ciphers in the problem located between the decimal point and first digit of both the multiplicand and multholier.

The words Product and Quotient on the base oi the Decimal and integral calculator are placed there for the .reason that the result of a n'iultiplication is termec product and when division is performed by multiplying the decimal of the divis r by the number to be divided the result is in this case a product, nevertheless, it is also the quotient, for the reason that the result obtained by the multiplication of the decimal produces the quotient. same as it divided in the usual way, as illustrated in the follow problem:

Multiplication; 24l-, 13fi, equals times.

It will be seen that this problem contains four integral. places. The first lclt digit of the multiplicand is 2 and the first leit digit of the product is 3. Turn the figure 2011 the dial until. it comes under or opposite the li; rure 3 on the base. The arrow in this-case will point to Zone of minus one and having: four whole numbers in the problem it will be seen that 4; minus 1 equals 3. The dcciu'ial point is therefore placed to the right of the bird digit from left of product.

Example #2 shows division cl (55.42 pounds of wheat by 60, showing that there are 1090 bushels and 20 pounds in the 65.420 pounds. Multiply the decimal oil 60 which is 016666666 by the gross number oi pounds 65,420. The first digit of the multiplicaud is l and the first digit of the product is also 1. These two digits brought opposite brings the arrow to point to Next figures. Now locate the next figure of the multiplicand on the dial, revolving that figure until it is opposite the cipher on the base. which is the next figure of the product the arrow will point to Zone of equal numbers. The ci lllll V to Zone of minus one,

" Fig.1 may, of course, be

This problem contains 8- numbers leaving 5, whole numbers for consideration. The first digit of the multiplicand is 1 and the first digit of the product or uotient is 7. By revolving the digit 1 on t e dial until it comes under the di it 7 of the product the arrow on the dial wi 1 point which means the decimal point is placed behind the 4th digit from the left of the product.

The preferred arrangement illustrated in varied, but in this arrangement the Zone of one less is at the left while the Equal number Zone is' at the right and Next figures zone is below the dial. Also the minus indication marks are at the left while the equal indication marks are at the right of the Next figures zone.

In the use of this improved device all 'mental calculations are made unnecessary and there are no exceptions to the general rules applied to its use. The novel relative arrangement of elements and indication marks are for simplicity of use, arranged in respect to the left-hand digits of the multiplicand and product, but may be arranged in respect to the digits of any one of the three factors, to wit: multiplier, multiplicand, and product. The present device has a further advantage over the device of my prior patent in that it is cheaper to construct.

The arrow on the revolving dial will only point to the words Next figures when the first digit of the multiplicand and the first digit of the product are one and the same. hen this occurs, the first digit of the multiplier may be compared with the first digit of the product and the arrow will indicate the location of the decimal point. The word Multiplier can be placed on the dial in connection with the word Multiplicand to read as follows: (Digits of the multiplicand or multiplier. The word Multiplier has been purposely omitted from the revolving dial to simplify the explanation and I will usually omit it from the commercial product, notwithstanding, that the co-action of the digits of the multiplicand and the multiplier with the-digits of the products usually produce one and the same results.

Vhat I claim is:

1. A decimal point calculator comprising a base, a dial mounted on said base, numerals on said base and dial, and co-acting indicating means on said dial and base, the relation of said numerals and indicating means being such that by aligning one of said numerals on said dial with one of the numerals on said base, said indicating means will determine the decimal point location in the product of which said numerals thus located are the left-hand digits of the product and one of the other factors.

2. A decimal point calculator comprising a base, a dial mounted on said base, numerals on said base and dial, and co-acting indicating means on said dial and base, the relation of said numerals and indicating means being such that by aligning one of said numerals on said dial with one of the numerals. on said base, said indicating means will determine the decimal point location in the product of which said numerals thus located are the left-hand digits of the multiplicand and product.

. 3. A decimal point calculator comprising a base,adial mounted on said base, digits circumferentially spaced on said dial and base, minus and equal indication marks on said base, and a pointer on said dial co-operating with said minus and equal indication marks substantially and for the purposes set forth.

1. The structure defined in claim 3 in which said base is also marked to indicate a Next figures zone with which thepoint er on said dial also co-operates for the purposes set forth.

5. The structure defined in claim 3 in which said base is marked on one side to in- I dlcate a Zone of one less and on the other a side is marked to indicate a Equal number zone.

p In testimony whereof I afiix my signature.

CHARLES E. LATSHAW. 

